package demo.mqserver;

import demo.common.*;
import demo.mqserver.core.BasicProperties;
import lombok.extern.slf4j.Slf4j;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

//消息队列本体服务器
//本质上是一个 TCP 的服务器
@Slf4j
public class BrokerServer {

    private ServerSocket serverSocket = null;

    //当前一个 BrokerServer 上只有一个 虚拟主机
    private VirtualHost virtualHost = new VirtualHost("default");

    //使用这个 哈希表 表示当前的所有会话（有哪些客户端正在和服务器进行通信）
    //此处的 key 是 channelId，value 为对应的 Socket 对象
    private ConcurrentHashMap<String, Socket> sessions = new ConcurrentHashMap<>();

    //引入一个线程池，来处理多个客户端的请求
    private ExecutorService executorService = null;

    //引入一个 boolean 变量控制服务器是否继续运行
    private volatile boolean runnable = true;

    public BrokerServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        log.info("[BrokerServer] 启动！");
        executorService = Executors.newCachedThreadPool();
        try{
            while(runnable){
                Socket clientSocket = serverSocket.accept();
                //把处理连接的逻辑丢给这个线程池
                executorService.submit(() -> {
                    processConnect(clientSocket);
                });
            }
        }catch (SocketException e){
            log.info("[BrokerServer] 服务器停止运行！");
            e.printStackTrace();
        }
    }

    //一般来说停止服务器，就是直接 kill 掉对应的进程就行了
    //此处的停止方法，主要适用于后续的单元测试
    public void stop() throws IOException {
        runnable = false;
        //把线程池中的任务都放弃，让线程都销毁
        executorService.shutdown();
        serverSocket.close();
    }

    //通过这个方法，来统一处理一个客户端的连接
    //在这一个连接中，可能会涉及到多个请求和响应
    private void processConnect(Socket clientSocket) {
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()){
            //此处需要按照特定格式来读取并解析，此时需要 DataInputStream 和 DataOutputStream
            try(DataInputStream dataInputStream = new DataInputStream(inputStream);
                DataOutputStream dataOutputStream = new DataOutputStream(outputStream)){
                while(true){
                    //1.读取请求并解析
                    Request request = readRequest(dataInputStream);
                    //2.根据请求计算响应
                    Response response = process(request, clientSocket);
                    //3.把响应写回到客户端
                     writeResponse(dataOutputStream, response);
                }
            }
        }catch (EOFException | SocketException e){
            //对于这个代码，DataInputStream 如果读到 EOF，就会抛出一个 EOFException 异常
            //需要借助这个异常来结束循环
            log.info("[BrokerServer] connect 关闭！客户端的地址：" + clientSocket.getInetAddress().toString() + ":" + clientSocket.getPort());
        } catch (IOException | ClassNotFoundException | MqException e){
            log.error("[BrokerServer] connect 出现异常！");
            e.printStackTrace();
        }finally {
            try{
                //当连接处理完了，需要关闭 socket
                clientSocket.close();
                //一个 TCP 连接中，可能包含多个 channelId，需要把当前这个 socket 对应的所有的 channel 也顺便清理掉
                clearClosedSession(clientSocket);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }

    private Request readRequest(DataInputStream dataInputStream) throws IOException {
        Request request = new Request();
        request.setType(dataInputStream.readInt());
        request.setLength(dataInputStream.readInt());
        byte[] payload = new byte[request.getLength()];
        int n = dataInputStream.read(payload);
        if(n != request.getLength()){
            throw new IOException("读取请求格式出错！");
        }
        request.setPayload(payload);
        return request;
    }

    private void writeResponse(DataOutputStream dataOutputStream, Response response) throws IOException {
        dataOutputStream.writeInt(response.getType());
        dataOutputStream.writeInt(response.getLength());
        dataOutputStream.write(response.getPayload());
        //刷新缓冲区
        dataOutputStream.flush();
    }

    private Response process(Request request, Socket clientSocket) throws IOException, ClassNotFoundException, MqException {
        //1.把 request 中的 payload 做一个初步的解析
        BasicArguments basicArguments = (BasicArguments) BinaryTool.fromBytes(request.getPayload());
        log.info("[Request] rid = " + basicArguments.getRid() + "， channelId = " + basicArguments.getChannelId() + "，type = " + request.getType() + "，length = " + request.getLength());
        //2.根据 type 的值，来进一步区分接下来这次请求要干啥
        boolean ok = true;
        if(request.getType() == 0x1){
            //创建 channel
            sessions.put(basicArguments.getChannelId(), clientSocket);
            log.info("[BrokerServer] 创建 channel 完成！channelId = " + basicArguments.getChannelId());
        }else if(request.getType() == 0x2){
            //销毁 channel
            sessions.remove(basicArguments.getChannelId());
            log.info("[BrokerServer] 销毁 channel 完成！ channelId = " + basicArguments.getChannelId());
        }else if(request.getType() == 0x3){
            //创建交换机。此时 payload 就是 ExchangeDeclareArguments
            ExchangeDeclareArguments arguments = (ExchangeDeclareArguments) basicArguments;
            ok = virtualHost.exchangeDeclare(arguments.getExchangeName(), arguments.getExchangeType(), arguments.isDurable(),  arguments.isAutoDelete(), arguments.getArguments());
        }else if(request.getType() == 0x4){
            //销毁交换机
            ExchangeDeleteArguments arguments = (ExchangeDeleteArguments) basicArguments;
            ok = virtualHost.exchangeDelete(arguments.getExchangeName());
        }else if(request.getType() == 0x5){
            //创建队列
            QueueDeclareArguments arguments = (QueueDeclareArguments) basicArguments;
            ok = virtualHost.queueDeclare(arguments.getQueueName(), arguments.isDurable(), arguments.isExclusive(), arguments.isAutoDelete(), arguments.getArguments());
        }else if(request.getType() == 0x6){
            //销毁队列
            QueueDeleteArguments arguments = (QueueDeleteArguments) basicArguments;
            ok = virtualHost.queueDelete(arguments.getQueueName());
        }else if(request.getType() == 0x7){
            //创建绑定
            QueueBindArguments arguments = (QueueBindArguments) basicArguments;
            ok = virtualHost.queueBind(arguments.getQueueName(), arguments.getExchangeName(), arguments.getBindingKey());
        }else if(request.getType() == 0x8){
            //销毁绑定
            QueueUnBindArguments arguments = (QueueUnBindArguments) basicArguments;
            ok = virtualHost.queueUnbind(arguments.getQueueName(), arguments.getExchangeName());
        }else if(request.getType() == 0x9){
            //发送消息
            BasicPublishArguments arguments = (BasicPublishArguments) basicArguments;
            ok = virtualHost.basicPublish(arguments.getExchangeName(), arguments.getRoutingKey(), arguments.getBasicProperties(), arguments.getBody());
        }else if(request.getType() == 0xa){
            //订阅消息
            BasicConsumeArguments arguments = (BasicConsumeArguments) basicArguments;
            ok = virtualHost.basicConsume(arguments.getConsumerTag(), arguments.getQueueName(), arguments.isAutoAck(),
                    new Consumer() {
                        //这个回调函数要做的主要工作，就是把服务器收到的消息可以直接推送回对应的消费者客户端
                        @Override
                        public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                            //先知道这个收到的消息要发给那个客户端
                            //此处 consumerTag 其实是 consumeId，根据 consumeId 去 sessionId 中查询，就可以获取对应的 socket 对象了，从而可以往里面发送数据了
                            //1) 根据 channelId 找到 socket 对象
                            Socket clientSocket = sessions.get(consumerTag);
                            if(clientSocket == null || clientSocket.isClosed()){
                                throw new MqException("[BrokerServer] 订阅消息的客户端已经关闭！");
                            }
                            //2) 构造响应数据
                            SubScribeReturns subScribeReturns = new SubScribeReturns();
                            subScribeReturns.setChannelId(consumerTag);
                            subScribeReturns.setRid("");  //由于这里只有响应，没有请求，不需要去对应，rid 暂时不需要
                            subScribeReturns.setOk(true);
                            subScribeReturns.setConsumerTag(consumerTag);
                            subScribeReturns.setBasicProperties(basicProperties);
                            subScribeReturns.setBody(body);
                            byte[] payload = BinaryTool.toBytes(subScribeReturns);
                            Response response = new Response();
                            // 0xc 表示服务器给消费者客户端推送的消息数据
                            response.setType(0xc);
                            response.setLength(payload.length);
                            response.setPayload(payload);
                            //3) 把数据写回客户端
                            //   此处的 dataOutputStream 这个对象不能 close
                            //   如果把 dataOutputStream 关闭，会直接把 clientSocket 里的 outputStream 也关了
                            //   此时就无法继续往 socket 中写入后续数据了
                            DataOutputStream dataOutputStream = new DataOutputStream(clientSocket.getOutputStream());
                            writeResponse(dataOutputStream, response);
                        }
                    });
        }else if(request.getType() == 0xb){
            //调用 basicAck 确认消息
            BasicAckArguments arguments = (BasicAckArguments) basicArguments;
            ok = virtualHost.basicAck(arguments.getQueueName(), arguments.getMessageId());
        }else{
            //当前的 type 是非法的
            throw new MqException("[BrokerServer] 未知的 type！type = " + request.getType());
        }
        //3.构造响应
        BasicReturns basicReturns = new BasicReturns();
        basicReturns.setChannelId(basicArguments.getChannelId());
        basicReturns.setRid(basicArguments.getRid());
        basicReturns.setOk(ok);
        byte[] payload = BinaryTool.toBytes(basicReturns);
        Response response = new Response();
        response.setType(request.getType());
        response.setLength(payload.length);
        response.setPayload(payload);
        log.info("[Response] rid = " + basicReturns.getRid() + "，channelId = " + basicArguments.getChannelId() + "，type = " + response.getType() + "，length = " + response.getLength());
        return response;
    }

    //遍历上述的 session hash 表，把该关闭的 socket 对应的键值对统统删掉
    private void clearClosedSession(Socket clientSocket) {
        List<String> toDeleteChannelId = new ArrayList<>();
        for(Map.Entry<String, Socket> entry : sessions.entrySet()){
            //集合类不能一边遍历，一边删除
            toDeleteChannelId.add(entry.getKey());
        }
        for(String channelId : toDeleteChannelId){
            sessions.remove(channelId);
        }
        log.info("[BrokerServer] 清理 session 完成！被清理的 channelId = " + toDeleteChannelId);
    }
}
